This is a very personal call. Some players will sharpen very frequently, such as every 2-3 hours of ice time. If you’re unsure of where to start, try getting them sharpened after 4-5 hours of ice time, and then adjust as you feel is necessary. It’s also worth noting that colder ice (especially the type found outdoors) is much harder, and will dull your skates very quickly. If you’re playing with your buddies on the outdoor rink, it’s probably a good idea to get a sharpening before your next game.